The overall goal of the project is to examine circadian rhythm processes underlying sleep and wakefulness and to evaluate the hypothesis that disturbances of circadian rhythms may play a major role in the development of sleep disorders. Using mus musculus as a model system for assessing circadian sleep-wake rhythms, we have shown that disturbances of the sleep-wake rhythms can be seen in animals having a clear-cut activity cycle. More recently, the techniques have expanded to permit a meaningful evaluation of the effects of aging on these rhythmic processes. We propose to pursue the project from three general points of view. 1) We will examine the sleep disturbances in light of prior history, lighting condition, and age. 2) We propose to evaluate the behavior of the underlying rhythm processes in an attempt to elucidate the properties of the oscillators. 3) We will assess age-dependent variations in state-dependent properties of the EEG and in rhythm processes that may account for changing distributions of sleep state and activity.